Two-cylinder short-wave resonator apparatus



Aug. 241, 1945. A, H RYAN v 2,383,343

TWO-CYLINDER SHORT-WAVE RESONATOR APPARATUS` Filed Aug. l5, 1940 lNvENToR /7/060/2/@00 ATTOR N EY Patented Aug. 2l, 1945 TWO-CYLINDER SHORT-WAVE RESONATOR APPARATUS Alden H. Ryan, Wilkinsburg, Pa., ass'ignor to Corporation,

Westinghouse Electric East Pittsburgh, Pa., a corporation of Pennsylvania Application August 13, 1944i, Serial No. 352,413

17 Claims.Y

For many purposes, in ultra-high-frequency work, the ability easily to change the frequency of hollow-conductor resonator-equipment, over a wide range of frequency-variations, is frequenti ,1. 1y extremely important, much more so thanA the efliciency of the apparatus. One example of such work is to .be found in dielectric-measurements; another, in frequency-measurements; and still another, in military communications, where the ability to change the wave length easily is of great importance for reasons of secrecy. One of the difliculties in previous types of conductorensheathed' hollow-body oscillators has resided in the difficulty of varying their wave lengths.

One of the objects of my invention, therefore, is to provide a new type of hollow-body resonator in which the wave length can be readily changed, and this new type of resonator is broadly useful, either with or without the frequency-varying adjustment, and either alone, or in combination with electron-stream apparatus for utilizing the resonator in an equipment in which the electronstream is velocity-modulated.

Another of the objects of myinvention is to provide a modied quarter-wave coaxial-cylinder resonator, or a resonator having two nested conducting cylinders of dierent diameters, disposed one within the other, both cylinders being closed at each end. and one cylinder being preferably shorter than the other, so that an end-space is provided which joins the annular resonatingspaces betweenthe two cylinders. The resonating-spaces are so excited that the resonator can be utilized as a combined buncher and catcher in an electron-beam oscillator or amplifier of a type in which the beam passes diametrically through the four walls of the vresonator in a line which is transverse to the axis.

A further object of my invention relates to means for very sensitively controlling the resonating frequency of such a resonator by provid.'- ing minute adjustments in the length of the outer cylinder, or in the spacing between the spaced end-walls of the outer and inner cylinders, respectively, the apparatus being very sensitive, in its resonating frequency, to very small adjustments of this nature.

Further objects of my invention have to do with various constructional details and arrangements of the general type of apparatus already mentioned. i

With the foregoingv and other objects in View, my invention consists in the structures, apparatus, combinations, circuits and methods herein- (Cl. Z50-27.5)

after described and claimed, and illustrated in the accompanying drawing, wherein:

Figures 1, 2 and 3 are longitudinal sectional views of three different forms of electron tubes embodying my invention; and

Fig. 4 is atransverse sectional view on the plane indicated by the line IV--IV in Fig. 31.

The illustrated forms of embodiment of my 'improved vacuum tube utilize an evacuated container comprising an outer metal cylinder 5 and an inner metal cylinder 5 of smaller diameter, disposed inside of the cuter cylinder 5. One end of the device is provided with a metal end-portion 1 which is integrally or hermetically united to the outer cylinder 5, and which also constitutes an end-closure for the inner cylinder 6. The other end of the outer cylinder 5 is provided with a flexible-walled portion 8 which is joined onto anA end-wall 9, so that said end-Wall 9 may be adjusted in an axial direction with respect to the rest of the outer cylinder 5. The exiblewalled portion 8 is shown in the form of an accordion-pleated member having thin metal walls which are joined, with vacuum-tight joints, to the cylindrical wall 5 and the end-wall 9 respectively. The axial adjustment of the end-wall 9 is controlled by means of a cross-piece I I which is adjusted by means of axially extending setscrews I2 and I3, abutting against suitable brackets Il on the outer cylinder 5. The end of the inner cylinder 5, opposite to the end-wall 1, is provided with a separate end-closure wall I5 of its own, said end-closure wall I5 being spaced axially from the end-wall 9 of the outer cylinder 5.

In the form of invention shown in each of the figures, the four cylindrical wall-portions comprising both sides of the outer and inner cy1inders 5 and 5, are provided with diametrically aligned openings I5, I1, I8 and I9, respectively,

disposed in a line extending transversely with re` In the illus- Y spect to the axis of the cylinders.

trated form of embodiment, the line of the openings Ii--IS is disposed approximately midway of the total length of the cylinder, corresponding to ace oscillation in' a fundamental mode of oscillation, although said line of openings I B-ll might be displaced in an Ioi center' relation, to correspond with a harmonic mode of oscillation in a manner which is described and clahned in my copending application Serial No.l 352,411, illed August 13, 1940, for High-frequency apparatus utilizing harmonically-energized-hollow-body resonators.

The emmen-many aligned openings ls and lle:

-other protuberance 22 is preferably provided with an insulated floating electrode 29 of carbon or other material having a secondary electron emissivity ratio materially less than unity, for the purpose of dissipating the beam of electrons which flows from the lament 25, so as to prevent such beam from impinging concentratedly upon the end-wall 24 of the protuberance 22, as describedand claimed in a copending application of G. L. Tawney, Serial No. 323,935, led March 14,

1940, and assigned to the Westinghouse Electric 8: Manufacturing Company.

A suitable accelerating-held, for the electrons emitted from the element 25, is provided by means of a variable battery 3| which is connected between a ground connection/32 of the outer cylin-l der 5, and one of the terminal-leads 21 of the filament 25. As a result of this accelerating electrostatic ield, the electrons emitted from the lament 25 are given an initial velocity whereby they enter the first opening I6 in the form of a to join to an external The strengthened oscillations of the catcher are tapped, by means of any suitable externalcircuit coupling-means' such as a half-loop 54' which terminates on the inside of the outer cylinder 5 and which has a conductor-35 which extends out through a vacuum-tight insulating sleeve 35. output-circuit 31 of any kind.

In the form of my invention shown in Fig. l,

the resonating-spacesl of the buncher and catcher merge into one another, both at the junctions of the annular spaces between the two cylinders, or

beam of moving electrons, said opening I5 serving 1 as a beam-focusing means, or any other more elaborate means being utilized, if desired, in accordance with known principles of electron-tube design. 'I'he beam of electrons then passes successively through the four diametrically aligned openings I5-I9, and finally is dissipated on the walls 22-24 of the second protuberance 22. The

first half of the resonating space between the two cylindrical members 5 and 5, that is, the space surrounding the intervening space between the iirst two openings I6 and I1, operates as a buncher for velocity-modulating the electrons of the beam as it passes through said intervening space from the opening I5 to the opening I1, such velocity-modulation resulting from the high-frequency electrostatic iield resulting from the resonating oscillations and extending in the general direction of the electron-flow. After passing through this intervening space between the holes -rather the two halves of the annular space between the two cylinders 5 and 5, and also at the transverse end-space between the inner and outer end-walls I5 and 9. In this manner, the oscillations induced in the catcher half of the resonating space are directly transmitted to the buncher" half of said space, thus constituting a certain feedback connection between the catcher and puncher, sothat some of the energy of the catcher is returned to the buncher to further `increase the velocity-modulation of the electronstream.

In some-cases it may be desirable tovprovide suitable baille-means for the purpose of controlling the oscillation-modes, and to that end I contemplate that suitable baiiles should be provided, as needed, either utilizing imperforate bales or perforated bailles. with the baiiles extending to any extent needed.

Thus in the form of my invention shown in Fig. 2, a longitudinally extending baille 45 is provided, running in an axial direction, in the form of a metallic partition betweenthe cylindrical walls of the inner and outer cylinders 5 and 5,

and extending across the end I5 of the inner cylinder, as indicated'.y at 4I. Preferably, the end portion 4I of the baille does not extendy into con- 40 tact with the end-plate 9 of the outer cylinder 5.

I5-I1 of the buncher, the velocity-modulated electron-stream then passes diametrically across the inner cylinder 5, until it reaches the third hole or opening I8. The intervening space bei tween the third and fourth holes I8 and I5 constitutes a part of a second resonating space which comprises the secondhalf or portion of the space between the inner and outer cylinders 5 and 5.

In this second resonating space, high-frequency energy is absorbed from the electrons of the beam, which have become bunched in their traversal of the diameter of the inner cylinder 5, said bunchling resulting from the alternate accelerations and decelerations which are imparted to the electronstream by reason of the high-frequency oscillations of the buncher. The second`resonatin`g space, or half-portion of the total resonating space between the outer and inner cylinders 5 and 5,'is thus utilized as a catcher wherein the oscillations are augmented from the high-frequency energy derived fromthe bunched electrons of the beam.

` which is shown in Figs. 3 and 4, I also show a` construction in which the two grids 45 and 49.

In the form of my invention shown in Fig. 2, the buncher and catcher resonating spaces are thus fairly well segregated from each other by means of the baille 40-4I, and additional feedbackmeans may be provided in the form of half-loops 43 which are disposed in the magnetic elds of the two resonating spaces, and electrically joined `together so as to couple said spaces together.

In the form of my invention shown in Figs. 3 and 4, two longitudinally extending shields 44 and 45 are provided on opposite sides of the inner cylinder 5, and extending between the inner cylinder and the outer cylinder 5, but extending less than the entire length of the inner cylinder 5, so that there may be no necessity for the special feedback coupling 43 which is shown in Fig. 2.

The four diametrically aligned openings I5, I1, I8 and I 9 may-be closed or covered by grids 46, 41, 48 and 49, respectively, said grids being diagrammatically illustrated as :metal-wire screens, although it is intended that such illus- Itration shall be symbolic of any open-work gridstructure such as is commonly known in the art oi' electron-tube design. I desire that the terms opening and grid shall be construed as synonymous with each other and interchangeable with each other, both terms being applicable either to a single opening or to a plurality of juxtapositioned openings. I

In the form of embodiment of my invention of the catcher are disposed more closely together, as measured in the line of movement of the electron-stream, than the corresponding grids 45 and `frequency rate;

41 of the buncher. This isin accordance with usually preferred constructional arrangement whereby the bunched electrons are paused to traverse the catcher more quickly than they do the buncher, thus enabling thecatcher to the better absorb nergy from the beam without running the risk of reducing the electron-velocity of some of the electrons to zero as the beam traverses the catcher.

Inail of the forms of embodiment of my invention, simple adjustment ofthe set screws. l2 and I3 serves to adjust the resonating frequency of the resonator over a wide frequency-variation, and thus serves as an exceedingly convenienttuning-means for the apparatus.

While I have shown my invention in .three different forms of embodiment, and in particular,

' in forms of embodiment as an oscillator or highfrequency oscillation-generator, I desire it to be understood that the general principles of my invention are susceptible of considerable variation and adaptation, as various changes and'modifications may be made rby those skilled in the art in applying the invention to other uses. I desire, therefore, that the appended claims shall be accorded the broadest construction consistent with their language.

I claimuas my invention:

1. An electron tube comprising an evacuatedv container; means therein for producing an electron-beam; a modulating beam-coupling means for operating on said electron-beam at a buncher-region thereof for modulating xthe electronvelocity of said beam at a predetemiined highan excitable beam-coupling means to be acted upon by said electron-beam at a catcher-region thereof for absorbing highfrequency energy from the modulations of said electron-beam successively first in operative relation to the beam-modulating portion and later in operative relation to the energy-absorbing portion of the resonating space of the resonator, said resonator comprising the two different portions of the resonating space in open-space communication Vwith one another, suiciently free of conducting partitions so that a high-frequency oscillating condition in the energy-absorbing portion of the resonating space will directly communicate a high-frequency oscillating condition to the beam-modulating portion of the resonating space; .and coupling means for coupling the resonator to some external device.

2. An electron tube comprising an evacuated container; means therein for producing an electron-beam; means for providing first, second and third spaces to be successively traversed by said beam; said iirst and third spaces being two diiIerent portions of a single conductor-ensheathed hollow-body resonator, said second space being of a drift-space length which causes the electrons to become bunched as a result of velocity-modulation in said iirst space, so that the electrons y `traverse said third space in a substantially bunched condition; the said resonator comprising two dierent portions of the resonating space in open-space communication with one another,

sumciently free of conducting partitions so that a high-frequency oscillating condition-in said third-space portion of the resonating space will directly communicate a high-frequency oscillating condition to the first-space portion o f the resonating space: and coupling means for coupling the resonator to some external device.

3. An electron tube comprising an evacuated container; means therein for producing an' elec- "tron-beam; means for providing rst, second,

third and fourth spaces to be successively trav-- ersed by said beam; lmeans adapted to be energized to produce a unidirectional potential-gradient for acting longitudinally uponA said beam somewhere within said first space; said second i and fourth spaces being two different portions of onatingspace will directly communicate a highfrequency oscillating condition to the secondspace portion of the resonating space; and coupling means within saidf'resonator for coupling the internal oscillations within said resonator to some external Idevice.

. 4. An electron tube comprising an evacuated container; means therein for providing a, source of emitted electrons; four successively mounted spaced grids therein for providing a first intervening space between the first and second of said four grids, a second intervening space between the second and third of said four grids, and a third intervening space between-the third and fourth of said four grids; said second space being of a length which causes the electrons to fbecome bunched as a result of velocity-modulation in saidA first space,- so that the electrons Vtrav-` erse said third space in a. substantially bunched condition; an electron-beam-producing means, including means adapted to be energized to produce a potential-gradient somewhere in the space between the electron-source and the iirst of said four grids, for imparting an initial velocity to the electrons and for causing a beam of electrons to flow successively .through the four aforesaid grids; a single conductor-ensheathed hollowbody resonator including said rst and third intervening spaces as two different portions of the resonating space of said resonator, the two different portions of the resonating space of the resonator being in open-space communication with one another, sufiiciently lfree of conducting partitions so that a high-frequency oscillating condition in the portion of the resonator including said third intervening space will directly communicate a, high-frequency oscillating condition tothe portion of the resonator including said rst intervening space; and coupling means within said resonator for coupling the internal oscillations within Vsaid resonator to some external device.

5. An electron tube comprising: a two-cylinder hollow-conductor resonator-element comprising two cylindrical members of different diameters, lthe larger cylindrical member' being hollow and substantiallyclosed at each end; the

` smaller cylindrical member being disposed within the larger cylindrical member and being smaller axially, as well as radially, than said larger cylindrical member, one end of the inner cylindrical member being spaced from the corresponding end or the outer cylindrical member; the four spaced cylindrical wall-portions o1' said two cylindrical members having substantially alined openings lying in an approximately diametrical line spaced a considerable distance away from said spaced end of the inner cylindrical member and extending transversely with respect to the axis of said resonator-element; means providing an evacuated container including said two-cylinder hollow-conductor resonator-element and including a space surrounding each of said diametrically alined openings in the outer cylindrical `member; means for producing an electron-beam well as radially, than said larger cylindrical member, one end of the inner cylindrical member being spaced from the corresponding end of the" outer cylindrical member; the four spaced cylin drical wall-portions of said two cylindrical members having substantially alined openings lying in an approximatelyv diametrical line extending transversely with respect to the Vaxis of said resonator-element at a point substantially midway of the length thereof; means providing an evacuated container including said two-cylinder hollow-conductor resonator-element and including a space surrounding each of said diametrically alined openings in the outer cylindrical'member;

' means for producing an electron-beam for passing' successively through said four wall-openings within said evacuated container; and coupling means for coupling to the internal oscillations within said two-cylinder hollow-conductor resonator-element. Y i.

7. Ari electron tube comprising: a two-cylin- `derl hollow-,conductor resonator-element comprising two cylindrical members of diilerent diameters. the larger cylindrical member being hollow and having vacuum-tight end-walls, the smaller cylindrical member being disposed within the larger one; the four spaced cylindrical wallportions oi' said two cylindrical members having der hollow-conductor resonator-element comprising two cylindrical members of different diameters, the .larger cylindrical member being hollow and substantially closed at each end; the smaller cylindrical member being disposed within the larger one;v the four spaced cylindrical" wall-portions of said two cylindrical members having substantially alined openings lying in an approximately diametrical line transverse with respect to the axis; means providing an evacuated container including said two-cylinder hollow-conductor resonator-element and including l a space surrounding each of said diametrically alined openings in the outer cylindrical member; means for producing an electron-beam for passing successively through said four wallopenings within said evacuated container; the distance between the two wall-openings of the inner cylindrical member being of a length which causes the electrons to become bunched as a result of velocity-modulation in the precedingspace between the two cylindricall members; and coupling means for coupling to the internal oscillations within said ltwo-cylinder hollow-conductor resonator-element.

. 9. An electron tube comprising: va, two-cylinder' hollow-conductor resonator-element comprising two cylindrical members of diierent diameters, the larger cylindrical member Ibeing hollow and substantially closed at each end, the smaller cylindrical member being disposed within the larger one; the four spaced cylindrical wall-portions of said two cylindrical members having substantially aimed openings lying in an approximately diametrical line transverse with respect to the axis; a, grid across each of said Iour`wall-openings; the last two grids being spaced a shorter distance apart than the ilrst two grids; means providing an evacuated container including said two-cylinder hollow-conductor resonator-clement and including a space surrounding each of said diametrically alined openings in the outer cylindrical member; means for producing an electron-beam-'for passing successively through saidfour wallopenings within said evacuated containerthe second and third grids being spaced by a distance which causes the electrons to become hunched as a result of velocity-modulation in the space between the ilrst two grids; and coupling means for coupling to the internal xoscillations within said two-cylinder hollow-conductor resonator-element.

10. An electron tube comprising: a two-cylinder hollow-conductor resonator-element comprising two cylindrical members of different diameters, the larger cylindrical member` being hollow and substantially closed at each end, the

substantially Aalined openings lying in an approximately diametrical line transverse with respect to the axis; enclosure-means, including said hollow larger cylindrical member, and also including vacuum-tight hollow protuberances over said openings in said hollow .larger lcylindrical mem-A ber, providing an evacuated vacuum-tight container for said electron tube; means .for producingan electron-beam for passing successively through said four vwall-openings within saidi evacuated container; and coupling means for coupling to the internal oscillations within said two-cylinder `hollowconductor resonator-element. f'

8. An electron tube comprising: a two-cylinsmaller cylindrical member being disposed with- .in the larger one; the four spaced cylindrical wall-portions of said two cylindrical members having substantially alined openings lying in an approximately diametrical line transverse with respect to the axis; two longitudinally disposed conducting partitions disposed across some of the space between the inner and outer cylindrical members on diametrically opposite sides of the two-cylinder hollow-conductor resonator element approximately in a plane transverse with respect to the diametrical line of said four wall-openings; means providing an evacuated container including said two-cylinder hollow-conductor resonator-element and including a space surrounding each of said diametrically alined openings in the outer cylindrical member; means for producing an electron-beam for passing successively 'through said four wallropenings within said evacuated container; the distancebetween the two wall-openings of the inner cylindrical seid two-cylinder hollow-conductor resonator- A in the larger one; 'the four spaced cylindrical wall-portions of said two cylindrical members having substantially alined openings lying in an `approximately diametrical line transverse with` respect to the axis; two longitudinally disposed conducting partitions disposed across the major portion of the space between the inner and outer ,cylindrical members on diametrically opposite sides of the two-cylinder hollow-conductor res- `onator element approximatelyin a plane transverse with respect to the diametrical line of said four wall-openings, a coupling feedback means for coupling the internal oscillations in the resonating spaces on lthe two sides of said longitudinally disposed partitions; means providing an evacuated container including said two-cylinder hollow-conductor resonator-element and including a spacev surroundingeach of said diaY metrically alined openings in the outer-cylindrical member; means for producing an electronbeam for passing successively through said four wall-openings within said evacuated container; and Ycoupling means for couplingto the internal oscillations within said two-cylinder hollow-conducten resonator-element,

12'. An electron tube comprising: a'two-cylin der hollow-conductor resonator-element comprising two cylindrical members of dilerent diameters. the larger cylindrical member being hollow and substantially closed at each end, the smaller cylindrical member being disposed within the larger one and ving one end-closure wall spacedfrom the e -closurewalLof thelarger cylindrical member at one end of the two-cylinder hollow-conductor resonator-element whereby the two halves of the resonating space are joined together by a transverse space at said end; the four spacedcylindrical -wall-portions of said twocylindrical members having substantially alined openings lying in an approximately diametrical line transverse with respect to the axis; means providing an evacuated container including said two-cylinder hollow conductor resonator element and including a space surrolmding each of ameters, the larger cylindrical member being hollow and substantially closed at each end, the smaller cylindrical member being disposed within the larger one and having one end-closure wall spaced from the end-closure wall of the larger cylindrical member at one end of the twocylinder hollow conductor resonator element whereby the two halves of the resonating space are joined together by a transverse space at said end; an externally controllable movable means connected to said end of the resonator for adjusting the eiective capacity between said spaced i end-closure walls of the inner and outer cylindrical members; the four spaced cylindrical wallportions of said two cylindrical members having substantially alined openingslying in an approximately diametrical line transverse with respect to the axis; means providing an evacuated container including said two-cylinder hollow-conductor resonator-element vand including a space surrounding eachof said diametrically alined openings in the outer cylindrical member; means for producing an electron-beam for passing successively through said four wall-openings within said evacuated container; the distance between the two wall-openings of the inner cylindrical member being of a length which causes the elec'- trons to become bunched as a result of velocitymodulation in thelpreceding space between the two cylindrical members; and coupling means for coupling to the internal oscillations within said two-'cylinder hollow-conductor resonatorelement.

14. An electron tube comprising: a two-cylinder hollow-conductor resonator-element comprising two cylindrical members of diilerent diameters, the largercylindrical member being hollow and substantially closed at each end, the smaller cylindrical member being disposed within the larger one and having one end-closure wall spaced from the end-closure wall of the larger cylindrical member at one end of the two-cylinder hollow-conductor resonator-element, means movably joining the outer one of said spaced end-closure walls to the cylindrical wall-portion of the'outer cylindrical member whereby it can be moved ina substantially axial direction. with respect to said two-cylinder hollow-conductor resonator-element; the four spaced cylindrical wall-portions of said two cylindrical members having substantially alined openings lying :in an approximately diametrical line transverse with respect to the axis; means providing an evacuated container inclding said two-cylinder hollow-conductor-resonator-element and including means for producing an electron-beam for passing said diametrically alined openings lnuthe outer cylindrical member; means for producing an electron-beam for passing successively through said four wall openings within said evacuated container; the distance between the two wallopenings of :the inner 'cylindrical member being of a length which causes the electrons to become bunched as a result of velocity-modulation in the preceding space between the two cylindrical members; and coupling means for coupling to the internal oscillations within said two-cylinder hollow-conductor resonator-element.

13. An electron tube comprising: a two-cylinder hollow-conductor resonator-element comprising two cylindrical members of diierent di- .successively through said four wall-openings V drical member being of a length which causes the electrons to become hunched as a result of a I velocityemodulation in the preceding space bespaced i' from thelend-closure wall of the larger cylindrical member at one end o f the two-cylinder hollow-conductor resonator-element whereby the two halves of the resonating space are joined together by a transverse space at said end; means `movably joining one of the end-wall portions oi said two-cylinder hollow-conductor resonatorelement to a cylindrical wall-portion thereof whereby said end-wall portion can b e moved in v a substantially axial` direction with respect to causes the electrons to become hunched as a' result of, `velocity-modulation in the preceding space between the two cylindrical members; and coupling means i'or coupling to the internal oscillations within said two-cylinder hollow-conductor resonator-element.

16. An electron tube comprising: a two-cylin-l der hollow-conductor resonator-element comprising two cylindrical members of diierent diameters, the larger cylindrical member being hollow and substantially closed at each end, the smaller cylindrical member being disposed within the larger one and having one end-closure wall spaced from the end-closurewall of the larger cylindricalv member at one end of the'two-cylinder hollowconductor resonator-element whereby the two halves of the resonating space are joined together by a transverse space at said end; 'said inner and outer cylindrical members being of metal, one section of the cylindrical wall-portion of the outer cylindrical member including an expansible andcontractible, vacuum-tight, ilexible-walled metallic part: the four spaced cylindrical wallportions of said two cylindrical members having substantially alined openings lying in an approximately diametrical line transverse with respect td the axis; means providing an evacuated container including said two-cylinder hollow-conductor resonator-element and including a space surrounding each or said diametrically alined openings inthe outer cylindrical amember, means i'or producing an electron-beam for pass successively through said four wall-openings within said evacuated container; the distance'between the two wall-openings of the inner cylindrical member being of a length which causes the elec element.

trons to become hunched as a result of veloclty`- modulation in the preceding space between the two cylindrical members; and coupling means for coupling to the internal oscillations within -said two-cylinder hollow-conductor resonatorelement. A

17.- An electron tube comprising: a'two-cylinder hollow-conductor resonator-element comprising two cylindrical members of different diameters, the larger cylindrical member being hollow andy substantially closedat each end, the `smaller cylindrical member being disposed within the larger one; thev four spaced'cylindrical wallportions or said two cylindrical members having substantially alinedvope'nings lying in an approximately diametrical line transverse with respect to the axis; a plurality of longitudinally .and approximately radially disposed conducting partitions between' the inner and outer cylindrical'members; means providing an evacuated container including said two-cylinder hollow-conductor resonator-element and including a space surroundingi each of said diametrically alined openings in the outer cylindrical member; means for producing an electron-beam for passing successively through said four wall-openings within said evacuated container; the distance between the two-wall openings'of the inner cylindrical members being of a length which causes the electrons to become'bunched as a result of velocitymodulation in the preceding space between the two cylindrical members; and coupling means fOr Coupling' to the internal oscillations within said two-cylinder hollow-conductor resonator- ALDEN H. RYAN. 

